<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .fu{
            overflow: hidden;
            width: 300px;
            height: 300px;
            border: 1px solid black;
            margin: 100px auto;
            
        }
        .zi{
            width: 300px;
            height: 300px;
            background-color: pink;
            transform-origin: left bottom;
            transform: rotate(180deg);
            transition: all 1s;
        }
        .fu:hover .zi{
            transform: rotate(0);
        }
    </style>
</head>
<body>
    <div class="fu">
        <div class="zi">你必须鼠标点我才能看到</div>
    </div>
</body>
</html>